I can give you the circumstances, a video will be slightly harder. I was at the shadow thrall/slow portion (right after the taken ogres and walking along the terraces) in shattered throne farming out my sunshot catalyst. After finishing it and wiping, I switched to graviton lance to finish out my cosmology kills cause trying to get them legit currently is stupidly tasking. when shooting the thrall the purple orb animation plays (as in you seem them turn into the perk thingy), however no explosion or cosmology seekers spawned, I wiped 3 times to see if it was just my game being stupid, however it did not fix the issue.